Re: Mechanism for helping in multi-channels configuration

[Simon Tournier]

Hi Attila,

On mar., 06 févr. 2024 at 17:16, Attila Lendvai <attila@lendvai.name> wrote:
>> The wishlist is: provide a machine-readable description on guix-science
>> channel side in order to help in finding the good overlap between
>> commits of different channels.
>
> i wrote about a missing abstraction here:
>
> https://lists.gnu.org/archive/html/guix-devel/2023-12/msg00104.html

You wrote in [1]:

        it's probably the same thing that causes the discrepancy between
        git commits and substitutes: the build servers are not building
        every commit of the git repo. they pick an unpredictable (?)
        series of commits, skipping some in between.  if i guix pull, or
        guix time-machine to the "wrong" commit, then i'll need to build
        some stuff locally. sometimes these can be heavy packages.

To my knowledge:

 + ci.guix (Cuirass) fetches every 5 minutes (IIRC) and builds the last
   commit.

 + bordeaux.guix (Build Coordinator) fetches the batch from the mailing
   list guix-commits:
   <https://lists.gnu.org/archive/html/guix-commits/2024-02/msg00795.html>

About CI, yes it is unpredictable.  About Bordeaux, it is not really. :-)

1: Re: Should commits rather be buildable or small
Attila Lendvai <attila@lendvai.name>
Sun, 10 Dec 2023 23:20:25 +0000
id:SXjFmdTgxwHYE-Z6t7SZOykuXMBiD454EF2uad96jGQemgJ6hXki_f1C7VxVHKHa4b7_j5UwJmffh_FiQqEz_bIYIBn9tpG4s9F7W1eIDAQ=@lendvai.name
https://lists.gnu.org/archive/html/guix-devel/2023-12
https://yhetil.org/guix/SXjFmdTgxwHYE-Z6t7SZOykuXMBiD454EF2uad96jGQemgJ6hXki_f1C7VxVHKHa4b7_j5UwJmffh_FiQqEz_bIYIBn9tpG4s9F7W1eIDAQ=@lendvai.name

> the git commit log is a too fine-grained granularity here. there
> should be something like a 'guix log' above the git log that could be
> used, among other things, to encode inter-channel dependencies.

Considering the current status and how substitutes are GC, the first
step would be the retention of some substitutes.  And thus the
specification for a policy of such retention.  It would allow to build a
database that could be queried by this hypothetical “guix log” – which
should be more something under “guix weather” IMHO.

For the interested readers, thread about retention:

    Building and caching old Guix derivations for a faster time machine
    Ricardo Wurmus <rekado@elephly.net>
    Fri, 10 Nov 2023 10:29:28 +0100
    id:87o7g29c94.fsf@elephly.net
    https://lists.gnu.org/archive/html/guix-devel/2023-11
    https://yhetil.org/guix/87o7g29c94.fsf@elephly.net

    Substitute retention
    Ludovic Courtès <ludovic.courtes@inria.fr>
    Tue, 12 Oct 2021 18:04:25 +0200
    id:87y26ytek6.fsf_-_@inria.fr
    https://lists.gnu.org/archive/html/guix-devel/2021-10
    https://yhetil.org/guix/87y26ytek6.fsf_-_@inria.fr

Although I concur with this need, I do not see how it would be help for
detecting compatibility between channels. :-)

Cheers,
simon